The common law has long been explained as a customary system of law, rooted in consent, whose rules are both consonant to reason and flexible, allowing the law to develop in accordance with the ‘felt necessities’ of the community. As such, it seems to have much in common with a law of nations founded on the consent of nations as well as reason, manifested in part by developing customary practices in the international community. Indeed, lawyers have gone so far as to state simply that the law of nations is part of the common law. In the words of Lord Denning:

Yet such a view has not been universally subscribed to. Many judges have taken a narrower approach, requiring norms of international law to be positively incorporated before they bind at common law. Nourse LJ, for instance, felt that established rules ‘derived from one or more of the recognised sources of international law’ are binding only when they have ‘been carried into English law by statute, judicial decision or ancient custom’.